Stimulus – a change in the external or internal environment that is detected by a receptor and brings about a response. Response – change in an organism due to a stimulus. Reflex – a rapid and “unconscious” response Require a precise pathway – at least 3 synapses Include 6 parts: >>>>>>>>>>>>>>>>>>> REFLEXES and REFLEX ARCS
Receptor – detects stimulus, transforms into an impulse Sensory Neurons – part of the PNS connects receptor to CNS thru dorsal nerve root Impulse travels freely along the axon Relay Neuron – receives messages from sensory neurons across synapses - passes them to motor neurons Within gray matter of spinal cord
Motor Neurons – Part of the PNS Carries impulse from CNS (relay neuron) to effector (muscle) Leaves thru ventral root of SC Cell body is in gray matter SC Gray Matter – region of synaptic connection in the SC Effector – carries out response
The mechanism of evolution- requires: Variations in phenotypes Genetic basis for variation Change in the environment Examples: 2 related to global warming: Sylvia atricapilla – Black Cap - migration Parus major – Great tit - breeding
MIGRATION PATTERNS Normal breeding – early summer across central and northern Europe. Then migrates to warmer areas before winter. Patterns show normal migratory pattern – Germany to Spain Recent studies – 10% migrating to the UK Experiments show that direction of migration is genetically inherited.
Breed in spring/early summer through Europe. Timing of egg laying is genetically programmed Day length determines time of year. Recent studies have shown that egg laying time is becoming earlier. Have greater reproductive success due to earlier opening of leaves on trees & biomass that feeds on the leaves – Biomass – food for the great tit!
Types of ReceptorsMechanoreceptor – pressure, texture, vibrations (ear)Chemoreceptors – chemical solutes and vaporsPhotoreceptors – react to lightThermoreceptors – change in temperature
Choroid – light absorbing pigment; stray light Retina – receptors for vision; rod cells Fovea – densely packed cone cells; acute vision Optic nerve – carries nerve impulses to brain Optic disk – blind spot Vitreous humor – supports eye; transparent Lens – focuses light Aqueous humor - supports eye; transparent Pupil – light enters here Iris – regulate size of pupil Cornea – outer layer; fixed focusing Sclera and conjunctiva – white; protects and supports Rod cells – black and white sensors; dark light Cone – color sensors; bright light
Rod cells Cone cells Light brightness Diversity of cellsWavelength sensitivityImpulse: neuron ratio distribution
Edge Enhancement – precentral nervous system;carried out on the retinaitself.
Gray areas – peripheral vision; fewer light sensitive cells Focused attention on any gray area – use center of the retina.
Contralateral Processing – is the way the brain collects and integrates information to create the perception of seeing.
Both eyes send information and sends to both sides of the brain.n Optic chiasm – where information crosses to the other side of the braine Both eyes are responsible for processing information from both eyes.
HOW DOES VISION WORK BLIND SPOTS OPTICAL ILLUSIONS
1. Eardrum – pressure waves causes the eardrum to vibrate2. Hammer, Anvil, Stirrup – eardrum pushes on bones of the middle ear; magnifies 20x.3. Oval Window – middle ear bones push on membrane ; causes cochlea to move4. Cochlea – pressure wave travels through fluid r Sensory cilia in cochlea move Causes the release of neurotransmitters between receptor and auditory nerve.s Auditory nerve – generates an impulse. Impulse is carried to the brain for translation________________________________________________ Semicircular canals – responsible for balance Eustachian Tube – functions to equalize air pressure and drains mucus Hearing Test
Learned Behavior Innate Behavior Experience Instinctive Modified by trial and Genetically based error Not modified Variation within Uniform throughout population population Affected by environment Unaffected by Capacity to learn may environment product of natural Beneficial behaviors selection rather than product of natural specific behaviors selection Learned or Innate??
INNATE LEARNED Sucking instinct Emotional expressions Training animals Birds hatching Walking Migratory patterns Learning to drive Hunting instinct Tying shoes Not breathing underwater Courtship and sexual behavior in species Reflexes – all Instincts
A directional response to a stimulus: Positive or Negative Chemotaxis – response to chemicals Phototaxis – response to light Gravitaxis – response to gravity Rheotaxis – response to water current Thigmotaxis – response to touch Paramecium
Response to a non directional stimulus: Humidity – a non directional stimulus Orthokinesis – speed of movement altered Klinokinesis – rate of turning
Allows an organism tochange or adapt inresponse to theenvironment which givesan increased chance ofsurvival
Non-associative Associative Habituation – repeated stimulus Imprinting – learned early in brings about decreased life – very receptive response. No reward or Forms instant bond with one punishment who provides the essential skills Sensitization – increased for survival response to a stimulus after a Conditioning – reward or punishing stimulus punishment Classical – PavlovianCrow Response Operant – behave to win award or avoid punishment Training A good example
1. Unconditioned Response – automatic to the stimulus (food elicits salivation)2. Neutral Stimulus – no response (bell ringing)3. Conditioning – neutral and unconditioned combined (dog associates bell with food and salivates)4. Conditioned Stimulus and Response (dog will salivate when bell rings – even without food)Example Example
Watch the video: To what extent do cowbirds learn their sons socially and how much is innate? Birdsong and Culture Birdsong Strong indicator of reproductive fitness Females select males based on RF Exaggerates traits - Lyre
How do neurons talk to each other?Through the SYNAPSE.Most are chemical. 2 main types: Excitatory – normal synapse. Neurotransmitter released by presynaptic neuron (axon) Causes positive ions to enter the post synaptic neuron (dendrite) Acetylcholine and dopamine Inhibitory Opposite effect – carry negative ions – Chloride - - into the post synaptic neuron. Increases polarization – hyperpolarization. Makes it difficult to produce an action potential Dopamine and GABA
Important Points: Axons of many neurons feed into the dendrite of the post synaptic neuron. Each axon contributes to a membrane potential. The effects of each can be excitatory or inhibitory. The effect is summative---- and if it reaches Threshold, an AP is propagated. Effects of excitatory neurotransmitters can be cancelled by inhibitory neurons. AP at postsynaptic neuron is determined by summation of messages.HOW IT WORKS!
Psychoactive DrugsAffect the brain and personality by either increasing or decreasing post-synaptic transmission.
Cholinergic vs. Adrenergic Cholinergic – Synapses using acetylcholine as the neuroT Acetylcholine – parasympathetic of PNS Importance in keeping “normalcy” Response = relaxing inhibitory Adrenergic – Synapses using noradrenalin as the neuroT Noradrenalin – sympathetic of PNS Importance for “alertness,” increased energy, & euphoria stimulant
Excitatory Drugs Nicotine – similar to acetylcholine --- fits in receptor Mimic excitatory neurotransmitters/ block inhibitor Is not broken down by enzymes - remains
Excitatory DrugsAmphetamines – stimulate release of noradrenalin and dopamine Moves directly into pre-synaptic neuron vesicle. Results increased awareness and energy
Excitatory DrugsCOCAINE –Normal Dopamine and adrenaline act as excitatory neurotransmitters Both usually taken back up at the pre synaptic axon or enzyme.With Cocaine Blocks receptors on the re-uptake pump NT/hormone remains and more is released Increases post-synaptic transmission Changes – Dopamine is a pleasure NT Euphoria, increased energy, alertness Highly addictive – body produces less natural dopamine
Inhibitory Drugs BENZODIAZAPINES (gamma-Aminobutyric acid) main inhibitory NT Enhance the effect of GABA (main inhibitory NT) Combines with and slows down GABA receptors on post-synaptic neurons Slows down brain activity.
Inhibitory DrugsAlcohol Initially acts as a stimulant Release of dopamine As level of BAC raises – has a sedative effect Increases binding of GABA Acts as an anesthetic
Inhibitory DrugsTetrahydrocannabinol Cannabis –Normal Dopamine and GABA proceed when neededWith THC THC inhibits GABA release GABA cannot inhibit dopamine Mood and Behavior Increased feelings of pleasure Intoxicated, hunger, memory loss, Used to treat nausea in cancer patients.
ADDICTION (Mouse Party) A chronic neurological disorder with: Genetic characteristics Psychosocial characteristics Environmental characteristics Changes in the brain result in compulsive desire to use a drug
General Causes of Addiction Genetic – not fully understood Different allele for a receptor? Carry modified versions of genes linked to drug metabolism Susceptibility does not mean inevitability. Psychosocial/ Environmental Peer pressure Timing Availability Legality/Religion Community Family Mental health